66551501221 has 4 divisors (see below), whose sum is σ = 66656971744. Its totient is φ = 66446030700.

The previous prime is 66551501207. The next prime is 66551501231. The reversal of 66551501221 is 12210515566.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 66551501221 - 2⁹ = 66551500709 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66551501231) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 52734315 + ... + 52735576.

It is an arithmetic number, because the mean of its divisors is an integer number (16664242936).

Almost surely, 2^66551501221 is an apocalyptic number.

It is an amenable number.

66551501221 is a deficient number, since it is larger than the sum of its proper divisors (105470523).

66551501221 is a wasteful number, since it uses less digits than its factorization.

66551501221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105470522.

The product of its (nonzero) digits is 18000, while the sum is 34.

The spelling of 66551501221 in words is "sixty-six billion, five hundred fifty-one million, five hundred one thousand, two hundred twenty-one".